Mobile computing continues to grow quickly as mobile devices, such as smart phones, add more power and more features. Users of such devices may now access various services on the internet, such as mapping applications, electronic mail, text messaging, various telephone services, general web browsing, music and video viewing, and similar such services. The small size of mobile devices may make it difficult to interact with such services, for example, because traditional mouse input is generally not practical with most mobile devices and the same is true for full-size QWERTY keyboards.
Many mobile devices now employ touchscreen interfaces as their main input mechanism. Such interfaces generally include an active display device and a touch sensitive overlay (e.g., a capacitive device that sense the contact or nearby presence of a user's finger). Mobile devices may also include a number of other sensors that can be used as input mechanisms, such as magnetometers (compasses) and accelerometers. For example, accelerometers can be used as input for games that are played on a device.